Systems, devices, and methods for preventing eyebox degradation in a wearable heads-up display

Abstract

Systems, devices, and methods for preventing eyebox degradation in wearable heads-up displays (“WHUDs”) are described. A WHUD may provide an eyebox defined by multiple spatially-separated exit pupils, where the size of the eyebox is influenced by the spacing between the exit pupils. A larger eyebox is achieved with larger spacing between the exit pupils but a larger spacing between exit pupils is susceptible to the formation of gaps or blind spots in the eyebox (eyebox degradation) if bright environmental light causes the user's pupil to constrict to a size that is smaller than the spacing between the exit pupils. A material of variable chromism is included in the user's field of view to reduce the perceived brightness of environmental light and thereby prevent the user's pupil from constricting to a size smaller than the spacing between the exit pupils.

The invention claimed is: 
     
       1. A method of preventing eyebox degradation in a wearable heads-up display, wherein the eyebox of the wearable heads-up display comprises multiple spatially-separated exit pupils at or proximate an eye of a user of the wearable heads-up display, the method comprising:
 positioning a material of variable chromism in a field of view of the eye of the user; and 
 varying an optical transparency of the material of variable chromism to compensate for variations in a brightness of an environmental light, wherein varying an optical transparency of the material of variable chromism in response to variations in a brightness of environmental light includes: 
 configuring the material of variable chromism with a first level of optical transparency while the brightness of the environmental light is at a first level of brightness; and 
 in response to the brightness of the environmental light changing from the first level of brightness to a second level of brightness, the second level of brightness brighter than the first level of brightness: 
 configuring the material of variable chromism with a second level of optical transparency, the second level of optical transparency less than the first level of optical transparency. 
 
     
     
       2. The method of  claim 1  wherein the material of variable chromism includes a photochromic material, and wherein configuring the material of variable chromism with a second level of optical transparency includes automatically configuring the material of variable chromism with the second level of optical transparency in response to the brightness of the environmental light changing from the first level of brightness to a second level of brightness. 
     
     
       3. The method of  claim 1  wherein the wearable heads-up display includes a photodiode, the method further comprising:
 detecting, by the photodiode, detecting variations in the brightness of the environmental light. 
 
     
     
       4. The method of  claim 3  wherein the material of variable chromism includes an electrochromic material and the wearable heads-up display includes a controllable current source, and wherein configuring the material of variable chromism with a second level of optical transparency includes varying, by the controllable current source, an electric current communicatively coupled to the electrochromic material.